Activation of protein kinase C-α is essential for stimulation of cell proliferation by ceramide 1-phosphate

Abstract 

We previously demonstrated that ceramide-1-phosphate (C1P) stimulates fibroblast and macrophage proliferation, but the mechanisms involved in this action have only been partially described. Here we demonstrate that C1P induces translocation of protein kinase C-alpha (PKC-α) from the soluble to the membrane fraction of bone marrow-derived macrophages. Translocation of this enzyme was accompanied by its phosphorylation on Ser 657 residue. Activation of PKC-α was independent of prior stimulation of phosphatidylinositol-dependent or phosphatidylcholine-dependent phospholipase C activities, but required activation of sphingomyelin synthesis. Inhibition of PKC-α activation also blocked C1P-stimulated macrophage proliferation indicating that this enzyme is essential for the mitogenic effect of C1P.

Abbreviations: C1P, ceramide-1-phosphate, ERK, extracellularly regulated kinase, FBS, fetal bovine serum, JNK, c-Jun terminal kinase, MAPK, mitogen-activated protein kinase, M-CSF, macrophage-colony stimulating factor, PBS, phosphate-buffered saline, PI3-K, phosphoinositide 3 kinase, PKB, protein kinase B, PKC, protein kinase C, PTX, pertussis toxin, BMDM, bone marrow-derived macrophages

Keywords: Ceramide 1-phosphate, Cell proliferation, Macrophage, Phosphoinositide-3-kinase, Protein kinase C, Sphingolipid